1. Field of the Invention
This invention relates generally to the selective control of weeds in grasses and, more specifically, to a Formulation and Process for the Selective Control of Bermuda and other grasses in Bentgrass, Kentucky Bluegrass, Dichondera, Fine Fescue, Tall Fescue, Annual and perennial Ryegrass and St. Augustinegrass turfs and Iceplant.
2. Description of Related Art
Bentgrass (agrostis palustris) is the grass of choice for golf course putting greens, lawn bowling surfaces and similar areas. It is particularly suitable for these applications for a number of reasons. Bentgrass turf can be mowed very low and it has good resistance to wear. A bentgrass turf can also be repaired fairly quickly by either seed or sprig (i.e. cuttings). Bentgrass is particularly useful in sunny, hot areas, as it grows best in full sun. Bentgrass is a perennial grass that "creeps," or propagates by stolons, or above-ground runners (see FIG. 1). Bentgrass turf is typically very dense.
St. Augustinegrass (stenotaphrum secundatum) is a popular grass for lawns on the gulf coast of the United States and Southern California, among other areas. St. Augustinegrass, like bentgrass, can be mowed low and is also a perennial that propagates by stolons.
Similarly, Kentucky Bluegrass, Dichondera, Fine Fescue, Tall Fescue, Annual and perennial Ryegrass are widely grown as turf grasses around the world; they generally are durable perennial grasses that may or may not propogate by stolons.
Most turf areas comprise various types of grasses. Golf courses, for example, will use bentgrass for the greens only. The fairways typically comprise other grasses, such as bermudagrass, fescues or even bluegrass. Golf course roughs could be a variety of grasses, which are typically not controlled, since it is desirable that the roughs be more difficult to play on (by design). The difficulty created by these segregated grass areas is that golfers and golf carts track from one area to the next in the course of a golf game. It would be common for a golfer to walk from a fairway, through a rough, and back onto the fairway, before then proceeding to the green. It is in this way that the different grass types may be tracked from one area to the next. These other grass types may also be carried over to other areas by the wind, animals, or even by over-seeding. All of these carryover mechanisms are particularly troublesome to the maintenance of putting greens.
Extreme care is taken of these putting greens. The putting surfaces are fertilized, rolled flat and smooth, and cut at least daily (if not more). Even minute defects in the putting surface can cause major problems for the golfers. A common problem arises when grasses, other than bentgrass, sprout on a putting green. Bermudagrass and the others are not as dense or fine-bladed as bentgrass, and therefore they interrupt the otherwise smooth surface of the bentgrass green. Furthermore, when grasses such as bermudagrass sprout on a putting green, there has been no prior way to selectively remove the "weed," or unwanted grass, without also damaging the surrounding bentgrass.
Bermudagrass (cynodon dactylon) is a warm season perennial that creeps by stolons, like bentgrass and St. Augustinegrass, and also by rhizomes (below-ground runners) (see FIG. 2).
Historically, greens keepers have dealt with bermudagrass invasions of bentgrass turfs by either cutting them out of the putting green or by killing them with some type of chemical grass killer, such as "ROUNDUP." In either case, various serious problems arise. Cutting out or chemically killing the undesirable grass leaves holes in the putting greens that must then be re-planted with either shoots or seeds of bentgrass, since bentgrass is not amenable to sod-laying. Since either method removes all of the turf in the area of the unwanted grass, the entire section is left totally bare of living grass. Many times there is perfectly healthy bentgrass interweaved with the offending grass that is also destroyed by these two methods. If there was a means for killing only the offending grass, such as the bermudagrass, without harming the bentgrass, the section would not be left totally bare. The result would be a quicker recovery from "weed" grass removal. For the golfing industry, this would mean significant savings, since the current practice frequently mandates the decommissioning of the damaged putting green while the holes are being repaired, sometimes for weeks. Furthermore, the selective removal process could be used preventively, i.e. applications could be made periodically to kill the bermudagrass, etc. before it takes a strong hold within the putting green.
A further problem with chemically killing all of the turf surrounding the unwanted grass is that there is inevitably a residue of chemical left in the soil. This residual chemical must be allowed to be completely absorbed by the soil before new grass seed or sprouts can be planted in the bare spot. This may result in delays lasting several days, in addition to the time needed for the new bentgrass to fill in again. A method of killing unwanted grasses in a bentgrass green, such as bermudagrass, that does not leave a residue that is harmfull to bentgrass would eliminate this problematical situation.
Other problems exist with current chemical grass killers. Most of these prior chemical grass killers include a petroleum-based surfactant. These surfactants are included to insure that there is good coverage of, and adhesion to, the leaves (or blades) of the grasses being treated. Without the surfactant, the grass-killing chemical is more prone to run off of the grass leaves and into the soil, where it is much less effective at killing the grass, since most of these chemicals are designed to be absorbed by the leaves. The roots of the grass will not absorb the chemical as effectively or as quickly as the leaves.
One problem with petroleum-based surfactants is that when the ambient temperature exceeds eighty degrees Fahrenheit (80.degree. F.), the surfactant tends to block the pores of the grass leaves. The blockage of the pores will prevent the leaves from absorbing nutrients, thereby damaging any grass plants where the petroleum-based surfactant has been applied. The result is that chemical grass killers containing these petroleum-based surfactants can only be safely applied during cool weather periods; this limits their utility severely, since it is typically desirable to apply the grass killing chemical during the hot summer months (i.e. when golf courses experience the most use).
Another problem with these petroleum-based surfactants is that petroleum is essentially a poison to most plant species, and therefore will by its nature harm the plants through its application. These petroleum-based surfactants should only be applied during periods when the grass is not in stress, i.e. not thirsting for water or hungry for nutrients. This limitation further narrows the utility of the chemical grass killers that include petroleum-based surfactants, because care must be taken not to apply them to plants that are in a weakened state. It would, therefore, be very beneficial to have a non-petroleum-based surfactant included with the grass-killing chemical, such as some sort of biodegradable material that does not harm the grass plants and therefore is not as limited in the ambient temperature range during which it can be safely applied.
These identical problems exist relative to Kentucky Bluegrass, Dichondera, Fine Fescue, Tall Fescue, and Annual and perennial Ryegrass Turfs as well as Iceplant, and a solution should also address these grasses and plants.